Magnesium bromide

Magnesium bromide[1]
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.246 Edit this at Wikidata
UNII
  • InChI=1S/2BrH.Mg/h2*1H;/q;;+2/p-2 checkY
    Key: OTCKOJUMXQWKQG-UHFFFAOYSA-L checkY
  • InChI=1/2BrH.Mg/h2*1H;/q;;+2/p-2
    Key: OTCKOJUMXQWKQG-NUQVWONBAY
  • [Mg+2].[Br-].[Br-]
Properties
  • MgBr2 (anhydrous)
  • MgBr2·6H2O (hexahydrate)
Molar mass 184.113 g/mol (anhydrous)
292.204 g/mol (hexahydrate)
Appearance white hygroscopic hexagonal crystals (anhydrous)
colorless monoclinic crystals (hexahydrate)
Density 3.72 g/cm3 (anhydrous)
2.07 g/cm3 (hexahydrate)
Melting point 711 °C (1,312 °F; 984 K) 172.4 °C, decomposes (hexahydrate)
Boiling point 1,250 °C (2,280 °F; 1,520 K)
102 g/(100 mL) (anhydrous)
316 g/(100 mL) (0 °C, hexahydrate)
Solubility ethanol: 6.9 g/(100 mL)
methanol: 21.8 g/(100 mL)
−72.0·10−6 cm3/mol
Structure
Rhombohedral, hP3
P-3m1, No. 164
octahedral
Thermochemistry
70 J/(mol·K)
117.2 J/(mol·K)
−524.3 kJ/mol
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
0
0
Safety data sheet (SDS) External SDS
Related compounds
Other anions
Other cations
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Magnesium bromide are inorganic compounds with the chemical formula MgBr2(H2O)x, where x can range from 0 to 9. They are all white deliquescent solids. Some magnesium bromides have been found naturally as rare minerals such as: bischofite and carnallite.[2][3]

Synthesis

Magnesium bromide can be synthesized by treating magnesium oxide (and related basic salts) with hydrobromic acid.[3] It can also be made by reacting magnesium carbonate and hydrobromic acids, and collecting the solid left after evaporation.[2]

As suggested by its easy conversion to various hydrates, anhydrous MgBr2 is a Lewis acid. In the coordination polymer with the formula MgBr2(dioxane)2, Mg2+ adopts an octahedral geometry.[4]

Uses and reactions

Magnesium bromide is used as a Lewis acid catalyst in some organic synthesis, e.g., in aldol reaction.[5]

Magnesium bromide also has been used as a tranquilizer[2] and as an anticonvulsant for treatment of nervous disorders.[6]

Magnesium bromide modifies the catalytic properties of palladium on charcoal.[7]

Magnesium bromide hexahydrate has properties as a flame retardant.[8]

Treatment of magnesium bromide with chlorine gives magnesium chloride. This reaction is employed in the production of magnesium chloride from brines.[9]

Structure

Two hydrates are known, the hexahydrate and the nonahydrate. Several reports claim a decahydrate, but X-ray crystallography confirmed that it is a nonahydrate. The hydrates feature [Mg(H2O)6]2+ ions.[10]

References

  1. ^ Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, Florida: CRC Press. pp. 4–67. ISBN 0-8493-0594-2.
  2. ^ a b c Gruyter, W. Concise Encyclopedia Chemistry, Walter de Gruyter & Company: Berlin, 1993; 612
  3. ^ a b Lewis, R.J. Hawley’s Condensed Chemical Dictionary, 15th ed.; John Wiley & Sons Inc.:New York, 2007; 777
  4. ^ Fischer, Reinald; Görls, Helmar; Meisinger, Philippe R.; Suxdorf, Regina; Westerhausen, Matthias (2019). "Structure–Solubility Relationship of 1,4-Dioxane Complexes of Di(hydrocarbyl)magnesium". Chemistry – A European Journal. 25 (55): 12830–12841. doi:10.1002/chem.201903120. PMC 7027550. PMID 31328293.
  5. ^ Evans, David A.; Tedrow, Jason S.; Shaw, Jared T.; Downey, C. Wade (2002). "Diastereoselective Magnesium Halide-Catalyzed anti-Aldol Reactions of Chiral N-Acyloxazolidinones". Journal of the American Chemical Society. 124 (3): 392–393. doi:10.1021/ja0119548. PMID 11792206.
  6. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  7. ^ Bouzide, Abderrahim (2002). "Magnesium Bromide Mediated Highly Diastereoselective Heterogeneous Hydrogenation of Olefins". Organic Letters. 4 (8): 1347–50. doi:10.1021/ol020032m. PMID 11950359.
  8. ^ Mostashari, S. M.; Fayyaz, F. (2008). "XRD characterization of the ashes from a burned cellulosic fabric impregnated with magnesium bromide hexahydrate as flame-retardant". Journal of Thermal Analysis and Calorimetry. 92 (3): 845. doi:10.1007/s10973-007-8928-4. S2CID 94416902.
  9. ^ Seeger, Margarete; Otto, Walter; Flick, Wilhelm; Bickelhaupt, Friedrich; Akkerman, Otto S. (2000). "Magnesium Compounds". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a15_595. ISBN 3-527-30673-0.
  10. ^ Hennings, Erik; Schmidt, Horst; Voigt, Wolfgang (2013). "Crystal Structures of Hydrates of Simple Inorganic Salts. I. Water-Rich Magnesium Halide Hydrates MgCl2·8H2O, MgCl2·12H2O, MgBr2·6H2O, MgBr2·9H2O, MgI2·8H2O and MgI2·9H2O". Acta Crystallographica Section C Crystal Structure Communications. 69 (11): 1292–1300. doi:10.1107/S0108270113028138. PMID 24192174.